The Constitution enables the federal government to impose and collect taxes via Article 1, Section 8 (also known as the "Taxing and Spending Clause"):
U.S. Const. art. 1, § 8, cl. 1.
In 1913, the Sixteenth Amendment was ratified, which enabled Congress to implement federal income taxes:
U.S. Const. amend. XVI.
Income Tax
Income tax is levied upon the money earned by individuals and corporations. Corporations must adhere to many of the same rules that individuals do, but also have additional requirements and rules schemes to cover the more complicated structure a corporation presents.
Gift & Estate Tax
Gift tax is tax levied on a gift, or combination of gifts, from one person to another that exceeds the annual exclusion amount. In addition to this annual exclusion amount, each individual has a lifetime applicable exclusion amount that can be used to avoid gift taxes as well as estate taxes. Estate tax being a tax levied on the property owned by an individual at the time of their death before distribution to the individual's heirs.
Payroll Tax
In addition to income tax, employers are subject to payroll taxes, which include Social Security, Medicare, and federal unemployment. Social Security tax and Medicare tax are imposed by the Federal Insurance Contributions Act (FICA). FICA taxes are applied to both employers and employees. Federal unemployment tax is derived from the Federal Unemployment Tax Act (FUTA). Only employers pay FUTA taxes.
Consumption Tax
Consumption tax refers to a tax relating to spending on goods and services. Types of consumption taxes include use taxes, sales taxes, excise taxes, value-added taxes (VAT), and taxes on imported goods. Consumption taxes are primarily used by the states (e.g., sales tax), however the federal government does employ excise (targeted) taxes on specific types of goods and services including alcohol, tobacco, certain firearms, and fuel.
